? about AWD, part time vs full time

[GTVR4]

I asked this on general but did not get much of a response so I figured it was technical enough to ask on this forum.

Could we change our AWD system from a full-time auto diff locking to a part time automatically engaging system? in other words to a system that would be FWD until slip is detected and then sends some torque to the rear. Like the diablo VT which is RWD until slip is detected then some power can be sent to the front. I read an article about AWD systems and it said that to get part time auto engaging auto companies used the Viscous Coupling (VC) or Torsen diff as the center differential where our VC is used as a diff lock. <----what exactly is that anyway?

What I wonder is if it was possible to convert our system would it aid in performance anyway? If its FWD until there is slip perhaps some of the drivetrain loss would be eliminated and we could better keep up with FWD and RWD cars from a roll? It would be great to have an AWD advantage from the start and not be hindered so much by AWD from a roll. Perhaps it could help durability if a max of say 25-30% could be applied to the rear.

This is all theoretical as I see it (at least as an application on our cars) and I'm no authority on AWD so give me some input here :).

[RabidDonkeyBoy]

perhaps some one else can confirm this but i belive either the Mighty Max or Colt Vista had a trans mission where you could change from fwd to awd. and i belive this trans can be swapped in pretty easily???? the only problem would be finding 1 and how much power it can handle before breaking..

when i was recently scavenging through the junk yard, there was a toyota tercel sr5 that you could do this with and also a few other weird settings could be done with with this car.

[RabidDonkeyBoy]

also, these center diffs in the GTR and i belive VTTT are electronically clutched diffs, so untill the ecu sees slippage the front wheels wont see power.

[shadow]

all awd / rwd / fwd / 4wd cars are 1 wheel drive.

our cars are FWD bais awd systems, meaning that the one wheel recieving power will be one of the front tires.

awd cars like the Lambo and the Skyline that you mention are RWD biased awd systems.

sorry to say but you will not eliminate any drivetrain loss unless you can avoid spinning up all the extra hardware for AWD. IE, the difference between FWD DSM and AWD DSM is that you have a driveshaft running from the front to the differential at the back. Then from the rear differential to the axles to the wheel hubs.

So awd vs fwd has this extra hardware:
1)mid differential
2)driveshaft
3)rear differential
4)2 more axles

having to spin these extra components is why AWD cars have higher driveline losses, as compared to FWD & RWD

to achieve the smallest driveline losses you need to go to a 4wd system. 4wd systems allow you to disengage the extra driveline parts at the mid diff - and at the tire hubs. So you eliminate #2,#3, and #4. However if you want to be able to engage all four wheels from this disengaged state while the car is moving you first have to bring #2,#3, and #4 up to speed before engaging other wise you'll feel like someone just threw out an anchor.

I do not see any easy way to do this. I know some sport utes have on-the-fly 4wd systems - you need to look into these. However all it sounds to me that these on-the-fly systems work by not disengaging the rear axles from the wheel hubs. This means you are still spinning up everything - just like you are in an awd system.

"It would be great to have an AWD advantage from the start and not be hindered so much by AWD from a roll."

the only way to do this is to disengage the awd system at the rear wheel hubs and the mid differential. that is the only whay it can be done - every other way and you are still spinning up #2,#3,#4.

This is just speculation on my part, but perhaps there is some rear diff which has clutches for both axles. This would allow the rear diff #3, and the driveshaft #2, not to be powered, you would still however have to spin up the 2 rear axles.

sorry to have to tell you this and take away the dream of AWD launches with FWD top-end :(

[Edited by shadow on 07-23-2001 at 12:46 AM]

[RyanV]

There is a difference between 4wd and awd?

[GTVR4]

So you're saying a different torque split doesn't make a difference? Its just the fact that there are more parts and more weight in AWD that soaks up the power, not the power that is applied to the front or rear? So basically if the AWD system was one that only engaged the driveshaft when the front wheels slip than you could have less drivetrain loss.

[BatmanGSX]

Originally posted by shadow
all awd / rwd / fwd / 4wd cars are 1 wheel drive.

our cars are FWD bais awd systems, meaning that the one wheel recieving power will be one of the front tires.

Afraid not. On a DSM 50% of the power is going to the rear differential as soon as the viscous coupling is fully engaged which is very fast. No variables are taken into account, if you are rolling under power, 50% of the power goes to the rear wheels automatically. If you were right we wouldn't need AWD dynos.

[Toast]

Originally posted by shadow
all awd / rwd / fwd / 4wd cars are 1 wheel drive.

Where are you getting this nonsense from??? If the tires are not slipping, then FWD/RWD cars are powering 2 wheels and AWD cars are powering 4 wheels. It's only when the wheels are slipping AND if there are open diffs present does this change. A FWD/RWD car with an open diff and (massively) spinning tires will send power to only 1 wheel. If an AWD car only has open diffs, then it too will send power to only 1 wheel assuming massive wheelspin. Of course, this changes depending on whether there are any locking diffs or electronic traction control. On our AWD cars with optional rear LSD, there is always a minimum of 3 wheels being driven (2 rear and 1 front). Without the rear LSD there is a minimum of 2 wheels being driven (1 rear and 1 front). Interestingly enough, you can have an AWD system using only open diffs and electronic traction control as done by Mercedes in their SUV.

our cars are FWD bais awd systems, meaning that the one wheel recieving power will be one of the front tires.

Once again this is nonsense. Power is split equally 50/50 front/rear and left/right. There is no inherent bias in the system. Most AWD systems function like this as it is easier and cheaper system to produce. Systems with a diffferent split (such as in some Porsches, Subarus, Skylines, etc) are more expensive to produce due to the differing diff design as well as supporting electronics being used.

Afraid not. On a DSM 50% of the power is going to the rear differential as soon as the viscous coupling is fully engaged which is very fast. No variables are taken into account, if you are rolling under power, 50% of the power goes to the rear wheels automatically. If you were right we wouldn't need AWD dynos.

This is incorrect. Viscous couplings are speed sensitive devices. They are not torque sensing devices like a Torsen/Quaife differential. When the viscous coupling locks up (well it never quite locks up) all it is doing is minimizing the speed difference between the 2 output shafts, not controlling power distribution. The actual power split depends on the ratio of traction available on both ends. The viscous coupling cannot sense or control this. It is just trying to limit the speed difference between the two output shafts.

[BatmanGSX]

Originally posted by Toast
Afraid not. On a DSM 50% of the power is going to the rear differential as soon as the viscous coupling is fully engaged which is very fast. No variables are taken into account, if you are rolling under power, 50% of the power goes to the rear wheels automatically. If you were right we wouldn't need AWD dynos.

This is incorrect. Viscous couplings are speed sensitive devices. They are not torque sensing devices like a Torsen/Quaife differential. When the viscous coupling locks up (well it never quite locks up) all it is doing is minimizing the speed difference between the 2 output shafts, not controlling power distribution. The actual power split depends on the ratio of traction available on both ends. The viscous coupling cannot sense or control this. It is just trying to limit the speed difference between the two output shafts.


Nothing that you addressed was said by me. I never said the viscous coupling controlled anything or did anything other than minimize the speed difference. By nature of the AWD system in our cars does 50% of the power, or close to it, go to the rear wheels.

It's 50/50 system because the viscous coupling was designed to make it that way. You can have a less agreesive viscous coupling that has less ability to sync up the rear wheels. The percentage of power the rear wheels sees is proportional to the speed difference between the front and rear output shaft. 100% of the speed of the front output shaft and the rear output shaft will see 50% of the power. This is what the system sees during normal cruising. Now if the rear output shaft was spinning at 50% of the speed of the front output shaft it would only see 25% of the power.

[Toast]

Originally posted by BatmanGSX
[QUOTE]Nothing that you addressed was said by me. I never said the viscous coupling controlled anything or did anything other than minimize the speed difference. By nature of the AWD system in our cars does 50% of the power, or close to it, go to the rear wheels. [quote]

Sure you did. I quote "On a DSM 50% of the power is going to the rear differential as soon as the viscous coupling is fully engaged which is very fast" That's completely untrue and the latter part of my post was aimed at explaining that. Whether or not you gave reasons for your statement doesn't change the fact that it's INCORRECT. In fact, if the viscous coupling is engaged, then the rear differential is seeing anything but 50%. It' just can't happen any other way. The only time the rear diff sees 50% of the power is when the viscous coupling is NOT engaged. If the center viscous coupling is engaged, then the rear diff is seeing some varying percentage above or below 50% depending on which wheels that are slipping.


[quote]Now if the rear output shaft was spinning at 50% of the speed of the front output shaft it would only see 25% of the power.

This example you gave is all mixed up. If the rear output shaft is spinning at 50% of the speed of the front output shaft, then it would be receiving more than 50% of the power. Why? Because that means the wheels connected to the front output shaft are spinning and thus turning faster and wasting power. The center viscous coupling would then in effect slow down the front output shaft and power is diverted to the rear output shaft where greater traction is available.

[BatmanGSX]

I think you are giving the abilites of the DSM viscous coupling too much credit. The device isn't really that effective. In almost all conditions will the power be divided up 50/50 front and rear. You can explain theories about viscous couplings all day long but if you have spent much time driving an AWD DSM you will know that it's a 50/50 spit 99% of the time.

[Toast]

Too much credit? Not effective enough? Do you really own an AWD DSM? Maybe you need to drive around in a FWD for a while to give yourself a reality check... If these VCs weren't "really that effective" then Mitsu wouldn't waste thousands of dollars putting these in.


In almost all conditions will the power be divided up 50/50 front and rear. You can explain theories about viscous couplings all day long but if you have spent much time driving an AWD DSM you will know that it's a 50/50 spit 99% of the time.

You can believe what you want to believe. I have no desire to keep beating anything into your head if you don't want to listen. But I'm curious... how does just driving around a DSM reveal the torque split? Does your car come with one of those nifty torque meters ala Skyline? Hell the simple act of going around a corner at any speed alters the torque split. And I'm sure most people turn the steering wheel more than 1% of the time they are driving...

[BatmanGSX]

What you are describing is A viscous coupler not THE viscous coupler in a DSM. All ours does is serve as a non locking way to couple the center differential to the rear differential. All these functions you are describing sound similar to the viscous couplings on Volvos and Porsches NOT DSMs. Did you read a description of a viscous coupling in a brochure for a 911 Turbo and think your DSM's works the same way?

[Edited by BatmanGSX on 07-23-2001 at 01:30 PM]

[shadow]

lol, stirred up a hornets nest huh? as long as all the tires are spinning at the same rate only 1 tire is actually doing all the work. this is especially true on open diffs.

DSM awd cars are fwd bias AWD, which means that until the fronts begin to slip the front wheels are doing all the hauling.... A 50/50 split in AWD DSMs is only possible when you spin out all 4 tires.

Batman.
"Afraid not. On a DSM 50% of the power is going to the rear differential as soon as the viscous coupling is fully engaged which is very fast. No variables are taken into account, if you are rolling under power, 50% of the power goes to the rear wheels automatically. If you were right we wouldn't need AWD dynos. "

I said NO SLIPPAGE - hence the couplings are disengaged.

Toast. Think about it. Flat straight surface. All tires rotating at the same rate. No turning. LSD(viscous not mechanical) or Open Diff. Only one tire is being driven - all the others are just keeping up. Sure, in real life what are the odds of having just one tire being driven for more than 3secs. Not much. Power is biased that way tho. Mechanical diffs are a lil different, depending on how they are constructed/designed the gearing shifts more power to the one that is not slipping, but they can be engaged (not 100%) only allowing slight amounts of slip (to account for turning). Mechanical diffs are also harder to turn - because the only allow a certain amount of slip. Quaiffe differentials allow you to decide the rate of slip on installation. I am not smoking crack, just give it a chance, think about it.

Toast: "Once again this is nonsense. Power is split equally 50/50 front/rear and left/right. There is no inherent bias in the system. Most AWD systems function like this as it is easier and cheaper system to produce. Systems with a diffferent split (such as in some Porsches, Subarus, Skylines, etc) are more expensive to produce due to the differing diff design as well as supporting electronics being used."

that first sentence is completely wrong - to have a perfect split like you are describing where each tire gets 25% power you need to have welded diffs. the mere fact that we have differentials allows for more power to go to one tire than the other. differentials (for the most part) while there is no slippage are only going to be powering one of their sides. Our cars do have bias - AWD dsms are FWD cars until the front tires begin to slip. Skyline is rwd until the rears begin to slip. AWD dsms also rarely reach 50/50 front/rear.

Toast, please just think about it for a sec.

[Edited by shadow on 07-23-2001 at 01:43 PM]

[BatmanGSX]

The AWD system in DSMs was specifically designed not to be FWD or RWD bias system. You don't know what the hell you are talking about if you think otherwise. I just got an e-test the other day and I watched the front and back rollers spinning at the same time from idle all the way up to 4500rpms. The front wheels are doing all the hauling until they slip, you make me laugh my ass off. Please just think about it for a second...

[Toast]

Originally posted by BatmanGSX
What you are describing is A viscous coupler not THE viscous coupler in a DSM. All ours does is serve as a non locking way to couple the center differential to the rear differential. All these functions you are describing sound similar to the viscous couplings on Volvos and Porsches NOT DSMs. Did you read a description of a viscous coupling in a brochure for a 911 Turbo and think your DSM's works the same way?


Where are you pulling this stuff from? What the hell is "THE" viscous coupler. They all act the same way. The difference in being how they are applied. Our VC acts to control the actions of the center diff. In other applications, the VC takes the place of a center diff. I surely know how the VC in a DSM works. As is, I have a nearly disassembled 1G AWD tranny sitting right in front of me. It sounds to me you are the one reading the sales brochures...

[BatmanGSX]

Originally posted by Toast
Originally posted by BatmanGSX
What you are describing is A viscous coupler not THE viscous coupler in a DSM. All ours does is serve as a non locking way to couple the center differential to the rear differential. All these functions you are describing sound similar to the viscous couplings on Volvos and Porsches NOT DSMs. Did you read a description of a viscous coupling in a brochure for a 911 Turbo and think your DSM's works the same way?


Where are you pulling this stuff from? What the hell is "THE" viscous coupler. They all act the same way. The difference in being how they are applied. Our VC acts to control the actions of the center diff. In other applications, the VC takes the place of a center diff. I surely know how the VC in a DSM works. As is, I have a nearly disassembled 1G AWD tranny sitting right in front of me. It sounds to me you are the one reading the sales brochures...

Fine. I'll be inclined to believe you a little more when you get that AWD tranny back in your car... But in any event, we now need to convince this other retard that an AWD DSM is not powered by 1 wheel.

[shadow]

you have no clue what I am saying do you? do you want me to explain it to you? Do you want me to go through how everything works on your AWD dyno? Do you?

[shadow]

"we now need to convince this other retard that an AWD DSM is not powered by 1 wheel"

you know dood, you are making a real horses ass of yourself. I suggest you quit the name calling, cool off a bit and re-read what I have written. Realize that I am specifying a specific situation of operation.

Just so that you get off my back I'll say this. An awd system with 3 LSDs has the ability to distribute power to all 4 tires dynamically and proportionally to traction. Without contradicting myself I can also say that the same car with 3 LSDs can have all the power diverted to a single tire. Furthermore, during cruise on the highway, under no acceleration, while not turning, it is most likely that only one wheel will be recieving power, whilst the other 3 are merely along for the ride.

[Edited by shadow on 07-23-2001 at 02:22 PM]

[Toast]

Originally posted by shadow
lol, stirred up a hornets nest huh? as long as all the tires are spinning at the same rate only 1 tire is actually doing all the work. this is especially true on open diffs.

Yep, stirred up a hornets nest. But it does make for interesting discussion... ;)

Unfortunately, I still disagree with you. 1 tire does not do all the work if all the tires are spinning at the same rate. I don't know where you are getting this from but it is WRONG. Lemme explain. Let's assume a FWD car. If both front tires are rotating at the same rate, then that means that the side gears (attached to each axle) in the front differential are NOT rotating in respect to each other. Meaning as the differential case is being driven by the ring gear, the axles are not rotating with respect to each other. That means that the spider gears are transmitting power to BOTH axles, not just one. Hence you are driving both wheels, not one. If you don't wish to believe me, then go read about it yourself. There's usually at least 1 or 2 detailed books that will explain how an open diff works in most libraries.

DSM awd cars are fwd bias AWD, which means that until the fronts begin to slip the front wheels are doing all the hauling.... A 50/50 split in AWD DSMs is only possible when you spin out all 4 tires.

That's absolutely wrong. Our AWD cars are based on a FWD platform car. But that means jack $h!t when it comes to our AWD systems. There is nothing in common btwn a FWD and AWD drivetrain and therefore I don't know where you are pulling this stuff from. Really, you need to study an AWD transmission before you keep repeating this...

I said NO SLIPPAGE - hence the couplings are disengaged.

Toast. Think about it. Flat straight surface. All tires rotating at the same rate. No turning. LSD(viscous not mechanical) or Open Diff. Only one tire is being driven - all the others are just keeping up.

No need to "think" about it or "rationalize" it. I explained how the system works above.

Mechanical diffs are a lil different, depending on how they are constructed/designed the gearing shifts more power to the one that is not slipping, but they can be engaged (not 100%)

Torsen type diffs can transmit 100% of the power. So can locked/welded diffs.

Quaiffe differentials allow you to decide the rate of slip on installation. I am not smoking crack, just give it a chance, think about it.

You're not smoking crack. But you still don't have your facts straight. BTW, Quaife diffs do NOT allow you to decide the rate of slip upon installation. Because they don't operate on the principle of slip, they are torque sensing. The clutch type differentials (KAAZ) allow you to preset the rate/max amount of lockup by varying the friction disk order prior to installation.

that first sentence is completely wrong - to have a perfect split like you are describing where each tire gets 25% power you need to have welded diffs.

No, to have this situation all that is needed is for every wheel to be moving at the same rate with a surplus of traction.

Our cars do have bias - AWD dsms are FWD cars until the front tires begin to slip. Skyline is rwd until the rears begin to slip. AWD dsms also rarely reach 50/50 front/rear.

This isn't the case. Really you need to study our AWD system in greater detail. You have a false notion of how it works. It's been rehashed over and over. Here and on the Talon Digest and I'm sure on a crapload of other sites. Do yourself a favor and do some research.

[BatmanGSX]

No, don't explain to me how it works... PLEASE. We don't need you giving out anymore false information. Please understand that the power from the engine is going to at least two wheels at the same time. It's possible to have a system like the one you are describing, it's all a matter of what order the power hits certain components of an AWD drivetrain. In the case of a DSM it is setup so that two wheels are under power. I know it's fun to bring up topics that were put to rest on the digest many years ago but it's only fun if you give the information that was found to be true, not the stuff that was not.

[shadow]

"That's absolutely wrong. Our AWD cars are based on a FWD platform car. But that means jack $h!t when it comes to our AWD systems. There is nothing in common btwn a FWD and AWD drivetrain and therefore I don't know where you are pulling this stuff from. Really, you need to study an AWD transmission before you keep repeating this... "

ok here is a layout, as I understand it of an AWD DSM - correct me if I am wrong. This is for the physical layout.

front differential - transmission shaft - differential - driveshaft - rear differential

the front and rear differentials are open the middle is a viscous diff.

start the car up, place in first gear, drive forward. at the point, all the tires are rotating at the same rate, so the middle differential is effectively disengaged. The driveshaft is spinning at the same rate as the transmission shaft (is there a better name for this?). So, effectively you are now only powering the front tires, the rears are along for the ride. Now go WOT - as the viscous coupling is not engaged yet the power goes to the front, the transmision shaft begins to rotate quicker than the driveshaft hence creating a difference in rotation of the two plates - this heats up the liquid in the middle differential making it more viscous, this now engages the driveshaft. Power is now transfered to the rear wheels. This all happens incredibly quickly, you might chirp your front tires before the diff engages. VC diffs do not engage fully (they cannot, by design, get the two shafts rotating at the same speed by itself), so you will still have more power going to the front tires. This is FWD bias AWD.

A RWD bias AWD system - like the skyline does the opposite of ours - the rear wheels are always engaged, and when the rear wheels slip - the front get some traction. Do you understand what I mean by biasing an awd car now?

"BTW, Quaife diffs do NOT allow you to decide the rate of slip upon installation" An issue of SCC has a Subaru Imprezza 2.5 RS that they are working on, they pruchased some Quaiffe LSDs, and the mechanic they had install the diffs asked the SCC dudes what rate they wanted. There were three rates, low, medium and high. Low was recommended for street. Medium for street/trak and high for track only. I'll dig up the magazine and quote directly from it if you like.

You're right, I have never looked at an open diff, nor seen the design of one, I assumed how it worked. I got the crazy idea that only one tire is being powered from this very board, a good friend, and a magazine, I believe it was Popular Mechanics, as they were explaining how an AWD system works. I remember reading it and going "that doesn't make any fucking sense, why have awd if only one tire is getting powered." Well, they elaborated and explained how it worked, they did not say that only one tire gets power through all driving conditions. Like I said before, during normal cruising on a highway you are most likely only getting power to one wheel. I am trying to explain it like they did, obviously very poorly.

I wish I could remember where exactly (which mag edition) I read all this, to make sure I am not missing some information that will allow it to make more sense. I remember perfectly that only one tire was being powered, as it was so odd for me to hear that.

I have the AWD system pretty well laid out, it's the damn open diff I'll have to read about.

[Edited by shadow on 07-23-2001 at 02:57 PM]

[BatmanGSX]

No, the center differential is not a viscous type and that is why you are confused. In addition to the THREE mechanical differentials the the AWD DSM has a viscous coupler.

[shadow]

isn't this what Toast is arguing with you about?

[BatmanGSX]

Yes, we were arguing about the viscous coupling, which the car has. The car also has front, center and rear mechanical differentials. Haven't you heard of breaking the spider gears in a center differential? Viscous differentials don't have spider gears... Do you have a FWD or something?

The power is going to the center and front differentials at ALL times, then the viscous coupler decides, via physics, how much power the rear wheel(s) see. The viscous coupler has no control over the front wheels as Toast seems to think, their rate is constant as that differential is mechanically tied to the transmission shaft. Then as the viscous coupler engages the rear wheels see more power until it is at a 50/50 rate. This happens very quickly, like a torque converter on an automatic transmission. As one side of the viscous coupler spins the other side will spin as well until both sides are spinning at the same speed. I don't know why you guys cannot understand this...

[Toast]

Originally posted by shadow
ok here is a layout, as I understand it of an AWD DSM - correct me if I am wrong. This is for the physical layout.

front differential - transmission shaft - differential - driveshaft - rear differential

It's hard to understand your idea of the AWD system without a better diagram. You've completely ignored the power input part of the transmission. But I'll get back to this shortly

the front and rear differentials are open the middle is a viscous diff.

That's not correct. The center differential has a mechanical open diff plus VC(not is a viscous if that's what you were implying). The rear differential CAN be open. But most AWD DSMs have a rear LSD although it is technically an option.

start the car up, place in first gear, drive forward. at the point, all the tires are rotating at the same rate, so the middle differential is effectively disengaged.

Whoa.... how did you jump to that conclusion? I think I see where you're mistaken. Power is introduced AT the center differential, not the front differential as you seem to assume. After power is introduced at the center diff, then it split to the front/rear and then to the left/right. You could not get by w/o the center diff. The car would go nowhere.


The driveshaft is spinning at the same rate as the transmission shaft (is there a better name for this?).

You completely skipped a few key components. Largest and most important being the transfer case. Your statement does not make sense if you can picture the layout of our trannies.

So, effectively you are now only powering the front tires, the rears are along for the ride.

Like I said before. Power is introduced at the center diff. The front or rear tires are not along "just for the ride" in this case.

Now go WOT - as the viscous coupling is not engaged yet the power goes to the front, the transmision shaft begins to rotate quicker than the driveshaft hence creating a difference in rotation of the two plates - this heats up the liquid in the middle differential making it more viscous, this now engages the driveshaft. Power is now transfered to the rear wheels.

Well this clearly demonstrates your ignorance of our AWD system (I'm pointing out a fact, not insulting you). We have both a mechanical center diff AND a VC that acts on the center diff. There are other AWD systems that use a VC as the center diff, but that is NOT how our system is designed. Furthermore, as I said the power is introduced at the center diff, of which its existence you are apparently not aware of.


A RWD bias AWD system - like the skyline does the opposite of ours - the rear wheels are always engaged, and when the rear wheels slip - the front get some traction. Do you understand what I mean by biasing an awd car now?

I think the more appropriate question is, do you understand now why everyone is telling you that you are wrong? :)


You're right, I have never looked at an open diff, nor seen the design of one, I assumed how it worked. I got the crazy idea that only one tire is being powered from this very board, a good friend, and a magazine.... I have the AWD system pretty well laid out, it's the damn open diff I'll have to read about.

Well, I think you owe it to yourself to do some more research on both subjects. After you understand how an open diff works, it's not too hard to understand how a clutch or viscous type LSD works. Torsen diffs are a little harder to understand but by no means a mystery if you bang your head hard enough. And if you want to argue (successfully) on this board, you should probably focus on our specific AWD system ;)

[BatmanGSX]

Toast is correct except for one thing:

The power is hitting the Front and Center Diff at the SAME time. An AWD car can drive around for a long time with a broken center differential because the front wheels will still turn. This will burn out the viscous coupler and transfer case but it can be done.

[Tevenor]

Don't jump to hard on me as I avoid tranny/driveline rebuilds like the plague.

I was under the impression, like Toast and Josh said, that the power was delivered to the center mechanical diff to be split to the front diff (which happens to be an open diff) and to the VC which decides how much power to send through the transfer case to the rear diff based on speed differentials. So if all 4 wheels are spinning at the same speed (per the original post examples), then the vc is not fully 'engaged' so the power split (at cruise) is more like 80% to the front open diff and 20% via the rears. When the vc desides to 'thicken' and transfer more power you get close to 50/50 split as the power is delivered to the center diff and then transferred via the front and the now almost fully locked vc.

Because the vc is so sensitive, you will always have some power being diverted to the rears just like you will never get the same advantage as a mechanical diff so in reality, you can never get a full 50/50 split (maybe 52/48???).

Just my thoughts. Let me know where I went astray.

-Sean

[Toast]

Originally posted by BatmanGSX
Toast is correct except for one thing:

The power is hitting the Front and Center Diff at the SAME time. An AWD car can drive around for a long time with a broken center differential because the front wheels will still turn. This will burn out the viscous coupler and transfer case but it can be done.

Bah... Where are you getting this from??? At the same time? Power must go through the center diff first! It cannot hit the front and center diff at the same time, there is NO connection that makes this possible. All power going to either the front or rear diff must FIRST go through the center diff. It's not an option... Let me explain this simply. You still don't understand how the damn tranny is layed out. Let's start from the tranny. Power is transmitted through the input shaft, through whatever gear you're in, through the intermediate gear, and ultimately to the center differential case. Then the path of power splits. At this point, power transmitted by the spider gears to one of the side gears in the center diff case transmits power through the front output shaft to the front diff. At the same time, power transmitted by the spider gears to the other side gear transmits power through the center shaft, xfer case, etc and reaches the rear diff. That's how the damn AWD system works.

Anyhow, I'm done beating this dead horse. I've told you how the tranny works. There's really nothing else I can do except slap you upside the head with tranny parts until this registers. I suggest that you take apart a tranny and if you haven't already read both the service manual and the tech manual then do so. Just about everything is outlined in there so you'll eventually see what I'm talking about.

[BatmanGSX]

My bad, I was going by Turbo Magazine's Project Talon, but they were running without a T-case, not center diff. Can you rewrite how the tranny is laid out again but include the viscous coupler please. It will make this thread worthwhile if you do. PLEASE?

[Toast]

Originally posted by Tevenor
I was under the impression, like Toast and Josh said, that the power was delivered to the center mechanical diff to be split to the front diff (which happens to be an open diff) and to the VC which decides how much power to send through the transfer case to the rear diff based on speed differentials.

Well your example is slightly flawed. Power does not exactly "transmit" through the VC and the VC does not really "decide" how much power to send to the xfer case. Lemme try to explain this for you. Power is transmitted from the center diff, through the center shaft, to the xfer case and eventually to the rear diff. The VC acts to limit the difference in speed between the center diff case and the center shaft. If there is no speed difference between the center shaft and the center diff case, then the VC is not called into play. If the case starts spinning faster or slower than the center shaft, then the VC starts to lock up. By doing so, it is forcing the center shaft and the center diff case to rotate at the same rate. By doing so, it indirectly forces the center shaft and front output shaft to spin at the same rate (assuming the spider gears are intact :) ) and thereby it slows down any spinning wheels. Hope that came across clear enough.

So if all 4 wheels are spinning at the same speed (per the original post examples), then the vc is not fully 'engaged' so the power split (at cruise) is more like 80% to the front open diff and 20% via the rears. When the vc desides to 'thicken' and transfer more power you get close to 50/50 split as the power is delivered to the center diff and then transferred via the front and the now almost fully locked vc.

No. If the VC is NOT engaged, then the split is 50/50. That is how the AWD system is designed. Hell, it is even outlined in GREAT detail in the Tech Manual. I suggest you read that first and then come back to this post. It will make much more sense. Hell, anyone who hasn't done so already should review the tech and service manual. It answers most of the questions that come up....

[Tevenor]

Originally posted by Toast
Well your example is slightly flawed. Power does not exactly "transmit" through the VC and the VC does not really "decide" how much power to send to the xfer case. Lemme try to explain this for you. Power is transmitted from the center diff, through the center shaft, to the xfer case and eventually to the rear diff. The VC acts to limit the difference in speed between the center diff case and the center shaft. If there is no speed difference between the center shaft and the center diff case, then the VC is not called into play. If the case starts spinning faster or slower than the center shaft, then the VC starts to lock up. By doing so, it is forcing the center shaft and the center diff case to rotate at the same rate. By doing so, it indirectly forces the center shaft and front output shaft to spin at the same rate (assuming the spider gears are intact :) ) and thereby it slows down any spinning wheels. Hope that came across clear enough.

Yeah I got it. So the flaw is in my thinking of how VC actually works in our cars, not necessarily the pathing of that power.


No. If the VC is NOT engaged, then the split is 50/50. That is how the AWD system is designed. Hell, it is even outlined in GREAT detail in the Tech Manual. I suggest you read that first and then come back to this post. It will make much more sense. Hell, anyone who hasn't done so already should review the tech and service manual. It answers most of the questions that come up....


So we have a driveline that effectively is 50/50 at all times until such time as there a speed differential between the front and rear or more specifically, the center shaft and the center case. At that time the VC locks to restore the 50/50 split, acting as a traction control device.

I have read the tech manual enough that its pretty much torn apart :) but not in enough detail about this particular subject (obviously). I an still slowly learning more and more. Suspension and engine/turbo theory were two areas I needed to make sure I fully understood first, now its the driveline's turn, hence my questions here.

Toast, thanks for the patience. I do have more questions but they are based on torque distribution w/ open diff's vs LSD's. Until I think I can ask an intelligent question on that topic, I will just go do some more reading. :D

[Toast]

Originally posted by BatmanGSX
My bad, I was going by Turbo Magazine's Project Talon, but they were running without a T-case, not center diff. Can you rewrite how the tranny is laid out again but include the viscous coupler please. It will make this thread worthwhile if you do. PLEASE?

Well since you said please... :)

Actually, I think I've covered it pretty well from the last post. But I'll go over it in a little more detail. As I've already stated, the center shaft is the connection between the center diff and the path to the rear diff. The function of the VC is to limit the speed difference between the center shaft and the center differential case. Here's how it's laid out. You can think of the VC as having 2 separate parts. These would be the

1. Housing
2. Hub

These can rotate independently of each other. Attached to each are disks annd between them lies viscous fluid. Obviously, as they rotate independently of each other, the viscous fluid will thicken and start to lock the two pieces together. Now the entire VC unit is attached to the rear of the center diff, around the center shaft. The Housing of the VC is attached to the center shaft. The Hub of the VC is attached to the center diff case. If the center shaft starts spinning fast or slower than the center diff case, then the VC starts to lock up. Now what happens? Assume the center diff case and center shaft are rotating together. Now the spider gears are also frozen in place and therefore the front output shaft must also spin at the same speed as the center diff case and the center shaft. That's how the VC operates. It locks up and indirectly controls the front output shaft. Hope this made sense to everyone.

[ProjectGSX]

This thread is funny. :)

[shadow]

"Like I said before. Power is introduced at the center diff. The front or rear tires are not along "just for the ride" in this case."

I have seen pics of the tranny - there are two diffs in the AWD tranny housing, one at the front and one at the back. From what I remember the transmission shaft is attached to both diffs. The front dif is mechanical open and the back one is limitied-slip.

So another diagram:

engine - clutch - transmission and gearing - the tranny has 3 (right?) shafts running down the length of the housing, one from the clutch, one which contains gears, and one more which is what I have been refering to as the transmission driveshaft - the transmission driveshaft has an open diff at the front and a limited slip at the back.

So if you are looking at the actual tranny housing there is one diff at the front and one at the back. Open diff means that you will at least be running one tire. Now, my flawed concept of the limited slip on DSMs is that it engages when slippage, or difference of rotation is detected between the two shafts.

[Tevenor]

Originally posted by ProjectGSX
This thread is funny. :)

"You think I'm funny? I'm funny to you? I'm a clown to you?"

:D God I love that movie....

[Edited by Tevenor on 07-23-2001 at 04:49 PM]

[Toast]

Tevenor, it sounds like you've got the idea now! :) I'd like to clarify one small but important detail. When the VC locks up, it is not restoring a 50/50 power split. Instead it is transferring power from one end to another. This isn't exactly obvious so let me clarify with an example.

Let's assume for an instant that the front wheels have completely lost all traction. Therefore the front output shaft starts spinning like mad and consequently the center shaft slows down. Most of the power is being sent down the front output shaft at this time. The VC senses this difference and locks up. Now the front output shaft and center shaft are spinning at about the same rate. However, since there is zero traction at the front wheels (and therefore zero load) almost all available power is sent through the center shaft and to the rear wheels. This example shows that the VC is a speed sensitive device. It reacts to speed difference and tries to keep everything rotating more or less at the same speed. But power will go to the shaft with greater load (traction).

[Tevenor]

Originally posted by Toast
Tevenor, it sounds like you've got the idea now! :) I'd like to clarify one small but important detail. When the VC locks up, it is not restoring a 50/50 power split. Instead it is transferring power from one end to another. This isn't exactly obvious so let me clarify with an example.

Like I said, I just give me some time and I can learn anything. :D



Let's assume for an instant that the front wheels have completely lost all traction. Therefore the front output shaft starts spinning like mad and consequently the center shaft slows down. Most of the power is being sent down the front output shaft at this time. The VC senses this difference and locks up. Now the front output shaft and center shaft are spinning at about the same rate. However, since there is zero traction at the front wheels (and therefore zero load) almost all available power is sent through the center shaft and to the rear wheels. This example shows that the VC is a speed sensitive device. It reacts to speed difference and tries to keep everything rotating more or less at the same speed. But power will go to the shaft with greater load (traction).

I thought I would throw this into it.

Viscous Coupling Schematic
http://members.theglobe.com/Tevenor/images/vc.gif
Rear Differential and VC on a Evo V
http://members.theglobe.com/Tevenor/IMAGES/EVO_NEW01.JPG

[Edited by Tevenor on 07-23-2001 at 05:20 PM]

[shadow]

You can only reach that page via a link on the very same website. They have it set up so that you have to be on their site browsing. They want to stop people from doing what you are trying to do :)

[Tevenor]

Originally posted by shadow
You can only reach that page via a link on the very same website. They have it set up so that you have to be on their site browsing. They want to stop people from doing what you are trying to do :)


Yeah I know. I spend my days building the same damn systems so I know how to get around them as well. But it usually isn't worth it, as in this case soooo....there you go.

[GTVR4]

Wow, I guess I better check on my posts more often :).

As I understand it, our cars have a 50/50 front/rear torque split when all wheels are spinning at the same speed. Power is first sent to the center diff which is a diff with the VC on the end. It is then transfered to the front and rear diffs which are open with the exception of the rear LSD on some cars (which is a VC unit as well). Then to the axles.

Power in, for example, acceleration is transfered to the rear wheels because as the front of the car gets light there is less traction on the front tires requiring less force to spin them. As those tires begin to lose traction the VC viscosity increases (I'm guessing here) and it acts like a glue trying to minimize the rotational difference between the two shafts, the driveshaft to the rear diff and the front output shaft <---(not sure about what that is called and this is part of our system that is still confusing to me).

Its a little easier to picture how the system works in a car that was originally RWD like my father's QX4 where you can see that there is a driveshaft going to the front wheels (yeah, I know its not exactly the same as our AWD). I have the DSM technical manual via the backup cd and I still can't picture how the power is transfered to the rear and the front at different speeds. Reading through the manual it shows that the center diff case has a pinion gear and two side shafts one going to the front which goes to the front output shaft and one going to the rear which goes to the center shaft. The VC is connected to the center shaft and the center diff case. I'm confused :).

The manual keeps talking about how the VC works to limit the differential action by the center diff. What in laymans terms does that mean? I think the term differential action is throwing me off.

What I was hoping in asking my original question was that there would be a way to replace our center diff and VC with a VC or torsen diff that could be very FWD biased, like 80/20 or ideally 100/0 and the diff would only send power to the rear wheels when the front wheels slip. So what I want is a different torque split if and only if that has any positive effect on the power that the car can put to the ground. I would think going down the road with a 50/50 split under no slip would be less efficient than going with something like an 80/20 split, am I wrong? Why?

[Boosted3000GT]

What about those trannies that Magnus Motorsports (I think, or is it TRE?) sells that lets you switch from FWD to AWD? I was thinking about getting one of those but I can find so little information on them. Do they work with the same clutches? (I obiously know very little about trannys)
Another question while I'm here. Does anyone make aluminum or carbon fiber driveshafts for these cars? What about axles? Anything better than stock floating around out there?Mike 93 3000GT VR-4

[Iceman21]

Originally posted by Boosted3000GT
What about those trannies that Magnus Motorsports (I think, or is it TRE?) sells that lets you switch from FWD to AWD? Mike 93 3000GT VR-4

They are made by Magnus Motorsports

[Toast]

Originally posted by GTVR4
The manual keeps talking about how the VC works to limit the differential action by the center diff. What in laymans terms does that mean? I think the term differential action is throwing me off.

Differential action in this case means simply allowing the two output shafts to rotate at different speeds. If you were to have a locked (aka welded) diff, then the 2 output shafts would be forced to rotate at the same speed all the time. The VC acts to limit the differential action. It allows some speed diff btwn the 2 shafts, but it doesn't let it get out of hand.

What I was hoping in asking my original question was that there would be a way to replace our center diff and VC with a VC or torsen diff that could be very FWD biased, like 80/20 or ideally 100/0 and the diff would only send power to the rear wheels when the front wheels slip.

Well I don't know of any units with bias to the front wheels. But there is one unit available that puts more bias towards the rear wheels. It's a Cusco Tarmac Gear Center Diff and it splits the power 35/65 F/R.

So what I want is a different torque split if and only if that has any positive effect on the power that the car can put to the ground. I would think going down the road with a 50/50 split under no slip would be less efficient than going with something like an 80/20 split, am I wrong? Why?

Just changing the torque split won't have any positive effects on the amount of power the car can put down. If you change the torque split to something other than 50/50, you are placing more load on one set of axles. Have you taken a good look at your AWD axles? They are very skinny. We already have a problem with breaking axles on high powered DSMs. It probably wouldn't help if we fed even more power to those axles ;)

You wouldn't gain much efficiency either by varying the torque split. Unless you can completely disconnect half of the 4WD system on the fly, you'll still have the same parasitic drag turning all the various driveline bits. So forget the idea of shift on the fly 4WD. Save that for the SUVs and worry about other more important things... like making more power :D

[Toast]

Originally posted by Iceman21
Originally posted by Boosted3000GT
What about those trannies that Magnus Motorsports (I think, or is it TRE?) sells that lets you switch from FWD to AWD? Mike 93 3000GT VR-4

They are made by Magnus Motorsports

They are NOT made by Magnus Motorsports. They come off a JDM Galant. I think from the 90-91 models but not 100% sure on that.

That tranny+xfer case combo just lets you put the power to the front wheels versus all 4 wheels (same effect as swapping in a welded VC and dropping the transfer case). It's not a shift on the fly part time 4WD system. You need to get under the car and remove 2 bolts to switch back and forth.

[Iceman21]

Originally posted by Toast

They are NOT made by Magnus Motorsports. They come off a JDM Galant. I think from the 90-91 models but not 100% sure on that.



Sorry I meant Magnus sells them

[Zazzster]

A semi related question. If I install a welded center diff, then the VC will no longer do anything. This is because the front and rear will always turn at the same speed. Right????

If you disconect the drive shaft, with a welded diff, then you can run on a FWD dyno. Right again????

If what I'm thinking is true, then with a welded center diff, If the front tires start to spin, the back tires will also spin at the same speed. ???????

Please let me know. I've read the entire thread, and I am pretty sure I understand. Just wanted to ask about the welded center diffs.

Anyone use them???
http://zazz6.tripod.com/gsx2.jpg



[Edited by Zazzster on 08-01-2001 at 04:30 PM]

[Kevin Jones]

There was this cartoon that I used to watch.
The bullwinkle show. Rocky and bullwinkle.
They had a little skit they did called "Mr. KNOW-IT-ALL"

Mr. KNOWITALL was played by bullwinkle and was a self acclaimed know it all who didn't know JACK S*&^ !

You guys have brought back memories of the old days when I use to have to take naps after watching this cartoon and eating lunch.

Please continue to amuse me as I am really enjoying this.

By the way, Shadow is correct. Not totally, but more than toast and batman.

You all have made valid points on certain aspects of your limited knowledge, but shadow seems to have the lead thus far through the fight.

GO SHADOW !

when you guys are done cat fighting, ask me, and I'll explain whats really going on with the DSM awd and it's comparison to other viscious coupled system.

have fun.

[DSMscreamer]

Well, If the DSM AWD system is front biased like shadow says, Why do the rear tires always break lose first on a hard launch? Then the fronts hook up. In the rain if I drop the clutch the rears can spin a good bit before the fronts kick in, and I have a LSD. Why is that?

[ShapeGSX]

Originally posted by DSMscreamer
Well, If the DSM AWD system is front biased like shadow says, Why do the rear tires always break lose first on a hard launch? Then the fronts hook up. In the rain if I drop the clutch the rears can spin a good bit before the fronts kick in, and I have a LSD. Why is that?

I don't know. My car doesn't react like that at all.

Generally the tire that is most likely to spin is the passenger side front tire. After going to the track, try and find the wheel-well with the msot rubber in it. It will be the passenger side front tire.

[DSMscreamer]

Nope, I've let my friend do a hard launch with my car in the rain while I watched from the outside and every time the rears broke first. Everybody I know with a high power DSM AWD says if they accelerate hard from a start going around a corner the car always fishtails which means rear wheel spin. In a front drive car if you accelerate hard in a turn the car pushes not fishtails. Next time its wet out do what I mentioned above and see what happens. Maybe each car is different in the way it reacts.

[ShapeGSX]

The rear end breaking loose in a turn has more to do with the suspension and camber curves than RW/FW torque bias.

As for your rear tires breaking loose in a straight line, I'm at a loss. Perhaps your car is lowered so much that you have horrible negative camber in the back. That will give you terrible traction, too.

Also, having a really soft suspension in the rear can cause the rear end to squat a LOT. This will cause the car to gain a lot of negative camber in the rear. That can also cause traction loss in a straight line. Particularly on 1Gs.

For drag racing, it is best to actually have a little positive camber in the rear so that when your car does squat, your tires will straighten out and give you a maximal contact patch. I wouldn't drive like that on the street, though! :)

Basically, the split IS 50/50 F/R. And the VC will lock up to almost 50/50. But torque will still be biased a little bit to the wheels that have the least traction.

So, evidently, your car has less traction in the rear, for some reason. :) Might want to have that looked at!

[Zazzster]

I would have to say that the fronts usally spin first. Whether or not you can see it happen or not. Goto TMOs web site and watch the red Talon lanuch.
http://www.tmo.com/prod/eprom/drag.shtml
My tires have 10k miles on them. The fronts are alot more worn then the rears. I know the front will wear because of turning, but I don't think thats the only cause for the uneven wear. I've done plenty of 360s in the snow. It always seems like the fronts spin first, and if the rears are spinning the fronts are definatly spinning.

This have been a great thread. A little rough, but I think that adds some spirit these discusions.

[BatmanGSX]

Originally posted by Kevin Jones
By the way, Shadow is correct. Not totally, but more than toast and batman.

Toast and I were right about the MOST important part, always have been. Shadow was the one who said the system is FWD bias and the rears are not under load until the fronts slip... that is DEAD WRONG. That is something that is extremely important to know the truth about if you are into road racing or AutoX, a car like that would need to be driven totally differently.

If you want to take my 14 second car on with your 11 second car on a road course I will still be able to eat you alive and ADHEM!!!!! Edit by RDY you out my tailpipe if you drive your car like it is FWD bias... sorry to sound harsh but you know how it goes...

Everything else... who gives a JOSH!!!! keep it clean!!? My car goes good.

[Edited by Rdy2race on 08-15-2001 at 05:30 PM]

[DSMscreamer]

Originally posted by ShapeGSX
The rear end breaking loose in a turn has more to do with the suspension and camber curves than RW/FW torque bias.

As for your rear tires breaking loose in a straight line, I'm at a loss. Perhaps your car is lowered so much that you have horrible negative camber in the back. That will give you terrible traction, too.

Also, having a really soft suspension in the rear can cause the rear end to squat a LOT. This will cause the car to gain a lot of negative camber in the rear. That can also cause traction loss in a straight line. Particularly on 1Gs.

For drag racing, it is best to actually have a little positive camber in the rear so that when your car does squat, your tires will straighten out and give you a maximal contact patch. I wouldn't drive like that on the street, though! :)

Basically, the split IS 50/50 F/R. And the VC will lock up to almost 50/50. But torque will still be biased a little bit to the wheels that have the least traction.

So, evidently, your car has less traction in the rear, for some reason. :) Might want to have that looked at!

That makes alot of sense. My suspension is stock and has 0ver 180,000 miles on it and I can tell it has gotten soft. It squats like an old style 300ZX when launching and I do have a fair amount of negative camber when the car is at rest. Ive learned a great deal about our AWD system reading this thread. I think the AWD in the old 88-91 Civic wagons worked like ours does but I'm not sure. Im suprised none of the turbo Hondas have tried using that drivetrain.

[Edited by DSMscreamer on 08-03-2001 at 11:40 PM]

[Toast]

All I can say is LAME...

New user jumps onto the board. In 2 or 3 days manages to post a couple of useless insulting posts. Adds fake timeslips to his sig. And manages to look like a complete ass.

Kevin Jones, you're obviously looking for some kind of response. Maybe you get off on such antics? Or maybe it's a way of lashing back at the world which obviously hasn't been treating you well? I suggest you go amuse yourself somewhere else. Come back when you're actually old enough to drive. If you're already that old, then that is pretty sad.

BTW, if you bother responding, try contributing to this thread instead of wasting bandwidth. Don't bother with the "ask me cause I know it all" BS. It doesn't float here.

[BatmanGSX]

Go get 'em tiger... I wanted to say that but I am a pussy. Hey Kevin Jones, where are you on the dsm.org timeslip page??? 11.2 my hairy, white ass.

[DSMscreamer]

I thought I smelled some BS too. Most guys that are running those times are pretty knowledgeable a woulds have something inteligent or at least usefull to say. Eveyone I know who runs 11s is damn near a DSM guru. Not to metion mature. So I pretty much ignored his post.

[MoBoost]

http://moboost.virtualave.net/DSMpics/Misc/awd.gif

[91-Tsi-Awd]

Completely off the subject, and on a lighter note...

Toast, have any other pics of your car? It's very tasteful and very good looking, I'd love to see more pics.

-End off Subject post, resume argument-

[Kevin Jones]

Originally posted by DSMscreamer
I thought I smelled some BS too. Most guys that are running those times are pretty knowledgeable a woulds have something inteligent or at least usefull to say. Eveyone I know who runs 11s is damn near a DSM guru. Not to metion mature. So I pretty much ignored his post.

dsm screamer, you cant always judge a book by its cover.
although you think you know most guys that run those times, I'm sure you've only read books about the majority of them.
whats hard for some people to accomplish may not be as hard for others. dont hate because you're not where the next guy is. eventually if you're patient and try to learn instead of try to burn, you will get there too.

Toast i wont respond by insulting you and im sorry you took my OPINION of who had a better handle of the knowledge of the coupling as an insult.

for your information, just because you see a new user name only proves that you, like everyone else, knows how to look at ones profile and make a judgement on the cover of a book.

wise up pal. i've been on this board for quite a while now.

Batman, you're right.

not about whos right and wrong. your car goes good for you and the next guy im sure is happy with his too.

[Kevin Jones]

Originally posted by BatmanGSX
Go get 'em tiger... I wanted to say that but I am a pussy. Hey Kevin Jones, where are you on the dsm.org timeslip page??? 11.2 my hairy, white ass.


go get em tiger? oh THATS real mature.

you wanted to say something but you're a pu$$y? I wont argue there.

because my timeslip isnt on someone elses page makes it not legit? hmmmmm you're making a whole lotta sense now.

i like my privacy and if too many people knew about what my car could do, then word would get out and i wouldnt be able to accomplish what i do on the weekends.

to some, streetracing is fun. to others, it's a business.

im somewhere in between and will take every advantage that i can. if a guy looks at my car and thinks he's not runnin faster than a 15.....lets race him for money. Im half way there. After i collect his money, my goal is accomplished.

timeslips are for people who want everyone else to think they are better than the next guy. i dont think i'm better than any other dsm'er on this board. i have helped many many people in my time and because you dont know me gives you no right to pass judgement.

no, i am not a guru, nor do you have to be to run a good time in a fast car. i am still in learning mode to put it modest. i will continue to assist where i can.

[vineet singh]

http://www.is300.net/forum_new/eek.gif... OMG ...http://www.is300.net/forum_new/eek.gif

Some of you need to sit down and read the free (aka $2.00) 1g DSM Technical Manual (http://www.ecanfix.com/~manualcd/main_3_gift.htm). Not only read it, but understand it, it tells you exactly how it works. I'm not going to say who's right, and who's wrong, but if you are humble enough, after you figure out why you are wrong, post it here.

There are other sections of the manual there too.

http://www.is300.net/forum_new/tongue.gif

[ippkiss]

they only thing i realy know about awd is that on subaru's "it transfers power from the wheels that slip to the wheels that grip." now if our system was biased one way or another the how come when i launch on dirt my both of my back tires instantly spin. i have thought alot about the awd system and why the front dosen't have a lsd, its there for a reason. when i launch on snow or dirt the two back wheels allwase spin, and the rear of my car slides of to one side, but only one of the front tires spins so the front end dosen't slide off, it just goes forward. that is very helpfull beacuse the car still goes straight forward even thought 3 wheels are spinning mad crazy. ever think what would happen to poor idiots like me if all four tires spun when you lunched it? i would have been stuck in a ditch a long time ago.

[DSMscreamer]

"dsm screamer, you cant always judge a book by its cover.
although you think you know most guys that run those times, I'm sure you've only read books about the majority of them.
whats hard for some people to accomplish may not be as hard for others. dont hate because you're not where the next guy is. eventually if you're patient and try to learn instead of try to burn, you will get there too."


On the contrary I know a number of people running low 11's and 10s and one in the 9's. I live around the corner from Extreme motorsports and have a lot of work done there. I get to speak to Sean and Terry pretty frequently and learn from thier knowledge and experience.As well a speaking to Jack and Rob and some of the Extreme staff to pick their brains and to learn more about the DSM.

I dont hate on anybody, especially on someone who has something constructive or inteligent to say as you obviosly didn't. You put yourself in a box with your own feeble comment. If you dont want people to judge you as ignorant then dont give them a reason to.

[BatmanGSX]

JOSH!!!!

OK you all know who this is directed to.

this is the rules

CLEAN!!! KEEP IT CLEAN!! meaning no F,S, GD, ( well I can bend on GD depending on when used. D words and such

I know you all mean well and I do agree with you on the KJ thing but let the mods deal with it and don't get put on the S&^T list ( see how easy that was!! :D ) I would hate to see it as most of you are major info sources.

The next post is on topic or this is closed and maybe removed. would be a DAM same but I do not have time to sift though 65 posts.

SO PLEASE do this and don't worry about KJ he has caused enough problems. kevin I ask you to contact me on the side i E mail form. I want this sorted out ASAP!!!

Dont make me put the SMACK DOWN on all of you LOL heheheh :D

Bill

Edit and removed BATMAN's post by Rdy2race

Like I SAID next post on topic and no more kj BS!!. Kevin I want a E mail!!! ASAP!!! enough of this waste of band with!!
BM-

[Edited by Rdy2race on 08-15-2001 at 05:47 PM]

[4G63Rydah]

About 4 or 5 months ago I was very interested in how differentials worked so I did A LOT of research on the subject and I have a pretty good understanding of how they work. Except for mechanical ones like the Quaife and Cusco. I was unable to find any pictures of their internals or descriptions so I don't know how they work but I know what they do.

I have read the entire thread and I have to say this. Shadow is WAAAAAYYY off and Toast and Batman were saying virtually the same thing except they disagreed on where power was coming in. (But now they agree on that subject). I'm not gonna start baggin on our 11 second wonder-boy so don't get excited yet Bill. ;)

Now. Toast has been right about pretty much everything he's been saying except for this following excerpt:

Originally posted by Toast
Let's assume for an instant that the front wheels have completely lost all traction. Therefore the front output shaft starts spinning like mad and consequently the center shaft slows down. Most of the power is being sent down the front output shaft at this time. The VC senses this difference and locks up. Now the front output shaft and center shaft are spinning at about the same rate.

Up to here the description is correct (except for where you said that the VC senses the speed difference and locks up. It doesn't "sense" anything and it never completely locks up. But I know that's not exactly how you meant it so I'll glance over that.

Let's continue with his quote where we left off, shall we..;)
However, since there is zero traction at the front wheels (and therefore zero load) almost all available power is sent through the center shaft and to the rear wheels. This example shows that the VC is a speed sensitive device. It reacts to speed difference and tries to keep everything rotating more or less at the same speed. But power will go to the shaft with greater load (traction).

This is COMPLETELY off. A viscious coupling is called a speed sensitive device because it locks up more as the speed difference increases between the housing of the differential and the output shaft. It's job is to try to equal out the power output as much as possible. It will never be able to completely lock up. And the only time the power is 50/50 (or virtually close to it) is when there is an excess of traction.

Saying that the "power will go to the shaft with greater load (traction)" is saying that it is a torque-biasing differential (i.e. a mechanical differential of the Quaife/Cusco veriety). Those types of LSDs actually transfer the power to the wheel with the most traction.

The VC (since it's a speed sensative device) simply makes sure that the speed difference between the housing of the differential and the output shaft isn't too different. As the differential housing and output shaft begin spinning at wildly different speeds (meaning one side is slipping) the speed of the discs (i'm talkin bout the internals of the VC now) greatly increases as opposed to the grooves in the VC. As this happens this also increases the amount of frictional heat which in turn increases the viscosity of the fluid in the VC. This makes the fluid thicker which makes it harder for the discs to spin past the grooves, which slows them down relative to the grooves. And this all means what? The output shaft and differential housing are now spinning at virtually (i say virtually because it isn't EXACTLY) the same speed. There is NO WAY for the VC to actually MAKE one side spin faster than the other. The only thing the VC will do when it's doing it's thing is slow things down. Meaning that it is balancing out the speed difference between the output shaft and differential housing.....

Now, shadow, where in the hell did you get this idea that our cars are always 1WD except for when one starts to spin out of control???? For open differential cars it is the EXACT opposite. So re-read that article and make sure you're EXACTLY sure of what you are saying. For all cars, open differential or not all the wheels that are being powered (meaning 2 on a 2WD, and 4 on a 4WD) are driving the car when there is an excess of traction. When there isn't enough traction is where differentials take effect. If our cars had 3 open differentials then yes, only one tire would spin...but ONLY (and yes i said ONLY) when there isn't enough traction. But since our cars have 2 LSDs (or 1 for some) 3 wheels will ALWAYS be spinning (2 for the people with one LSD).

[4G63Rydah]

Oh yeah, I forgot about one point... There was some talk about our cars being FWD biased. This is true to a VERY VERY small extent. But the reason it is true is not because of the differentials or anything. It's simple physics. There is more rotational mass for the rear part of the drivetrain then there is for the front part. So there will be a TINY bit more parasitic loss for the rear wheels. But I would be surprised if it was more (or even close) to 1 HP on a stock car.

If you think about it. The power goes through the gears of the trannies and hits the center diff (and yes the center diff gets the power first) which does it's best to split the power 50/50. At this point lets assume the power is EXACTLY split. So that means as the power is going to the front diff it is equal to that going to the t-case. As the power goes through the front diff and then consiquently the front axles parasitic losses will take their effect because of the rotational mass. The power going to the rear wheels however has to go through the t-case and the drive shaft before it gets to the rear diff. Parasitic losses will take their toll as the power arrives to the back. At which point it's still going to lose some more power going through the rear diff and rear axles.

here's a mathematical perspective:
Front power = power received from VC - power lost at diff (front) - power lost at axles

Rear power = power received from VC - power lost at t-case - power lost at driveshaft - power lost at diff (rear) - power lost at axles